432 research outputs found

    The electron-nucleon cross section in (e,ep)(e,e'p) reactions

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    We examine commonly used approaches to deal with the scattering of electrons from a bound nucleon. Several prescriptions are shown to be related by gauge transformations. Nevertheless, due to current non-conservation, they yield different results. These differences reflect the size of the uncertainty that persists in the interpretation of (e,ep)(e,e'p) experiments.Comment: 6 pp (10 in preprint form), ReVTeX, (+ 4 figures, uuencoded

    Nuclear currents based on the integral form of the continuity equation

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    We present an approach to obtain new forms of the nuclear electromagnetic current, which is based on an integral form of the continuity equation. The procedure can be used to restore current conservation in model calculations in which the continuity equation is not verified. Besides, it provides, as a particular result, the so-called Siegert's form of the nuclear current, first obtained by Friar and Fallieros by extending Siegert's theorem to arbitrary values of the momentum transfer. The new currents are explicitly conserved and permit a straightforward analysis of their behavior at both low and high momentum transfers. The results are illustrated with a simple nuclear model which includes a harmonic oscillator mean potential.Comment: 19 pages, revtex, plus 2 PS figure

    Are Hospital Efficiency and Quality of Care Affordable without External Revenue?

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    This qualitative study explored strategies academic research hospital administrators in Ontario, Canada, apply to generate nongovernment revenue to remain sustainable. The participants in the study consisted of senior-level academic research hospital executives with extensive experience in the subject area from major academic research hospitals, ranking the hospitals from highest to lowest in revenue generation. From this study, five themes emerged: working within the fiscal reality, the impact of the political environment, the focus on the mission, nongovernment revenue generation, and opportunities for the Ontario academic research hospitals. Findings from this study may contribute to discussions on implementing change by encouraging hospital executives to adopt a more coordinated and consistent approach to generating nongovernment revenue to support the mission of their hospitals

    Deep-ultraviolet cavity ringdown spectroscopy

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    The sensitive optical detection technique of cavity ringdown spectroscopy is extended to the wavelength range 197-204 nm. A novel design narrowband Fourier-transform-limited laser is used, and the technique is applied to gas-phase extinction measurements in CO2, SF6, and O-2. Further demonstration of the system capabilities is given in high-resolution recordings of the Schumann-Runge (0, 0), (1, 0), and (2, 0) bands in O-2. (C) 2004 Optical Society of America

    The off-shell electromagnetic form factors of pions and kaons in chiral perturbation theory

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    The off-shell electromagnetic vertex of a (pseudo-) scalar particle contains, in general, two form factors F and G which depend, in addition to the squared momentum transfer, on the invariant masses associated with the initial and final legs of the vertex. Chiral perturbation theory to one loop is used to calculate the off-shell form factors of pions and kaons. The formalism of Gasser and Leutwyler, which was previously used to calculate the on-shell limit of the form factor F, is extended to accommodate the most general form for off-shell Green's functions in the pseudoscalar meson sector. We find that chiral symmetry predicts that the form factors F of the charged pions and kaons go off-shell in the same way, i.e., the off-shell slope at the real photon point is given by the same new phenomenological constant β1\beta_1. Furthermore, it is shown that at order p4p^4 the form factor F of the K0K^0 does not show any off-shell dependence. The form factors G are all related to the form factors F in the correct fashion as required by the Ward-Takahashi identity. Numerical results for different off-shell kinematics are presented.Comment: TRIUMF preprint TRI-PP-94-4, 25 pages in LaTeX + 10 figures (uufile'd, compressed PostScript file appended at end, hardcopy available from authors

    Transverse QCD Dynamics Near the Light Cone

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    Starting from the QCD Hamiltonian in near-light cone coordinates, we study the dynamics of the gluonic zero modes. Euclidean 2+1 dimensional lattice simulations show that the gap at strong coupling vanishes at intermediate coupling. This result opens the possibility to synchronize the continuum limit with the approach to the light cone.Comment: 15 pages, LaTeX, 3 figures (7 PS files

    QCD near the Light Cone

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    Starting from the QCD Lagrangian, we present the QCD Hamiltonian for near light cone coordinates. We study the dynamics of the gluonic zero modes of this Hamiltonian. The strong coupling solutions serve as a basis for the complete problem. We discuss the importance of zero modes for the confinement mechanism.Comment: 32 pages, ReVTeX, 2 Encapsulated PostScript figure

    The Role of Final State Interactions in Quasielastic 56^{56}Fe(e,e)(e,e') Reactions at large q|\vec q|

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    A relativistic finite nucleus calculation using a Dirac optical potential is used to investigate the importance of final state interactions [FSI] at large momentum transfers in inclusive quasielastic electronuclear reactions. The optical potential is derived from first-order multiple scattering theory and then is used to calculate the FSI in a nonspectral Green's function doorway approach. At intermediate momentum transfers excellent predictions of the quasielastic 56^{56}Fe(e,e)(e,e') experimental data for the longitudinal response function are obtained. In comparisons with recent measurements at q=1.14|{\vec q|}=1.14~GeV/c the theoretical calculations of RLR_L give good agreement for the quasielastic peak shape and amplitude, but place the position of the peak at an energy transfer of about 4040~MeV higher than the data.Comment: 13 pages typeset using revtex 3.0 with 6 postscript figures in accompanying uuencoded file; submitted to Phys. Rev.

    A Gauge Invariant Unitary Theory for Pion Photoproduction

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    A covariant, unitary and gauge invariant theory for pion photoproduction on a single nucleon is presented. To achieve gauge invariance at the operator level one needs to include both the πN\pi N and γπN\gamma\pi N thresholds. The final amplitude can be written in terms of a distorted wave in the final πN\pi N channel provided one includes additional diagrams to the standard Born term in which the photon is coupled to the final state pion and nucleon. These additional diagrams are required in order to satisfy gauge invariance.Comment: 4 pages, LaTeX, 1 figure as a separate uuencoded compressed tar fil
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